Text Box: ACUTE LIFE THREATENING EVENT WITH RHABDOMYOLYSIS AFTER STARTING ON HIGH DOSE PYRIDOXINE THERAPY IN A INFANT WITH HOMOCYSTINURIA
Matsumori M, Shoji Yu, Noguchi A, Shoji Ya, Takahashi T, Takada G
Department of Pediatrics, Akita University School of Medicine, 
Akita, Japan

Objective: In-patients of homocystinuria with cystathionine beta-synthase deficiency, the biochemical response to relatively high dose of pyridoxine is usually examined to select treatments. Only liver dysfunction and sensory neuropathy have been described as adverse effects of a high dose, long-term oral administration of pyridoxine in CBS deficient patients. Here, we report a CBS deficient patient who showed acute life threatening event with myoglobinuria after a short-term administration of high dose-pyridoxine (500mg a day).
Results & Conclusions: Based on the clinical course in our case, acute toxicity caused by high dose of pyridoxine prescribed to an early infant was strongly suggested. Our patient showed compound heterozygote with the L539S mutation that is known to be responsive to pyridoxine, and the G307S mutation that is not responsive. When the G307S mutation, which is the most common mutation, is detected in a CBS deficient patient, we suggest that he should be treated by a low-methionine high-cystine diet without administration of pyridoxine, particularly in early infancy.
2015